Powder Ballistic Aerosol Marking (BAM) technology is a direct marking process, which is targeted to deliver solid toner particles on demand to a substrate, using an array of venturi structured pipes. Printing channels containing a venturi structure can provide a much collimated, high velocity gas stream to carry the printing material to the substrate. Currently, venturi structured BAM channels can be fabricated at 300 dpi resolution or higher (600 to 900 dpi) out of a polymeric photoresist material. The inner diameter of the channels typically ranges from 40 to 60 μm. In addition, high velocity gas jets enabled by the venturi convergence/divergence structure enable the gas stream of toner particles that exit the expansion pipes to remain collimated (in a narrow stream) well beyond the exit point of the pipes.
The original BAM concept was based on using high input air pressure of 100 psi or higher as the propellant to generate high velocity particles traveling at more than 200 m/sec. The kinetic energy of the particles is converted into thermal energy upon impact with the substrate and causes subsequent fusing of the particles directly onto the substrate. Kinetic fusing has been demonstrated for toner particles directly impacting a glass plate to produce a 3-dimensional pixel of piled toner. When extended to a plain paper substrate, toner capture by paper is typically very poor. As a consequence, in practice, toner is ejected onto an intermediate transfuse belt substrate, which captures all the ejected toner which is then subsequently transfused off-line.
A polymeric photoresist material for forming venturi structured channels is the preferred material over silicone not only due to material costs and ease of fabrication, but also because low cohesive BAM toners do not adhere to the walls of the channels as observed for silicone BAM channels. Although satisfactory in many respects, current BAM venturi configurations are in need of further development. Accordingly, there is a need for an improved venturi configuration particularly adapted for BAM applications.